1. Field of the Invention
The present invention relates to a radio communication apparatus, and, more particularly, to a movable or portable radio communication apparatus having communication capability with at least two communication systems.
2. Description of the Related Art
Conventional single radio telephone apparatus with two different communication capabilities includes, for example, a radio telephone apparatus described in Japanese Patent Application Laid-Open No. 7-177570 (hereinafter called the first reference).
The radio telephone apparatus described in the first reference has a cellular mode in the cellular system and a PHP mode in the personal handy phone (PHP). Either one mode is manually or automatically selected in use. For an incoming call, it is determined whether or not the incoming call is a PHP incoming call. If so, it is processed in a PHP system processing section. If not, it is processed in a cellular system processing section. On the other hand, for an outgoing call, radio wave from a PHP base station is measured for its intensity in response to an outgoing operation. It is determined from the result of measurement whether or not it is within a PHP service area. If not, it is notified to the user that the cellular mode is set. The user enters a telephone number after receiving the notification. On the contrary, if it is within a PHP service area, it is presented. Then, the user enters a telephone number after setting the PHP mode.
In addition, it is also disclosed that priority is previously set, that radio wave from a PHP base station is measured for its intensity after entering a telephone number in outgoing, that outgoing processing is performed in a PHP system processing section after setting the PHP mode if it is within a PHP service area, and that outgoing processing is performed in a cellular system processing section after setting the cellular mode if it is outside the PHP service area.
Thus, the radio telephone apparatus described in the first reference selects either one of the PHP mode or the cellular mode, and performs transmission by determining whether or not it is within a PHP service area by measuring intensity of radio wave from a PHP base station.
In addition, as a radio telephone apparatus for mode other than the PHP and cellular modes, for example, Japanese Patent Application Laid-Open No. 4-351127 (hereinafter called the second reference) describes a radio telephone apparatus that places an outgoing call by automatically changing over the mode between the cordless telephone mode and the portable telephone mode.
The radio telephone apparatus described in the second reference sends out a call request signal to a cordless telephone parent set in response to a calling operation by the user, and a dial signal to the cordless telephone parent set while fixing the mode at the cordless telephone mode when a call permission signal is received as a response signal from the cordless telephone parent set. On the other hand, if a call permission signal cannot be received, the mode is changed over to the portable telephone mode, and calling is made in the portable telephone mode.
The conventional radio telephone apparatus described above determines whether the telephone apparatus is within the service area of the system by measuring radio wave from a base station of one system, or detecting a call permission signal from a parent telephone set. If it is outside the service area, it is changed over to another system. Thus, the conventional radio telephone apparatus could automatically place an outgoing call to either one system by determining whether or not it is within the service area in outgoing.
However, the inventor of the present invention has first been aware of a problem when a line cannot be connected due to line congestion although the telephone apparatus is in the service area. That is, when a line cannot be connected although the apparatus is in the service area, changing-over cannot be automatically performed. Thus, it is necessary to manually change over the mode, and to enter a telephone number again.
In the current mobile communication, there is a possibility that connection cannot be established because a line becomes congested in some time zone as radio telephone terminals are rapidly spread. In such case, if changing-over is manually performed every time, operability is poor, and it is very inconvenient for the user.
In addition, when the circuit is disconnected as the user moves outside the service area during calling, or in other abnormal disconnection, it is necessary to manually change over the mode if calling can be performed on another system, and to enter a telephone number again. It makes operability very poor.